Unable to compile code containing generics and inner classes

Question

I am trying to implement a Singlely Linked List. I can not compile the following code. I removed a lot of unnecessary code that does not apply to this question from the snippet below:

public class SinglyLinkedList<T> { public SinglyLinkedList() { } private SinglyNode<T> _head = null; private class SinglyNode<T> { public T Data { get; set; } public SinglyNode<T> Next { get; set; } } private class Enumerator<T> { public Enumerator(SinglyLinkedList<T> list) { _list = list; //#1 _head = list._head; //#2 } private SinglyLinkedList<T> _list = null; private SinglyNode<T> _head = null; } } 

Statement marked # 2 fails with error - Cannot implicitly convert type 'SinglyLinkedList<T>.SinglyNode<T>' to 'SinglyLinkedList<T>.SinglyNode<T> Program.cs

The statement labeled # 1 is semantically similar to # 2 and compiles. What makes a program compile? Are there any general rules related to native + inner classes that make the above code not compile?

Please note that the above code snippet is part of my training by reinventing the wheel and not being production code.

Answer 1

Inner classes declare their own completely different T

Just remove T from inner classes and everything will be fine:

 public class SinglyLinkedList<T> { public SinglyLinkedList() { } private SinglyNode _head = null; private class SinglyNode { public T Data { get; set; } public SinglyNode Next { get; set; } } private class Enumerator { public Enumerator(SinglyLinkedList<T> list) { _list = list; //#1 _head = list._head; //#2 } private SinglyLinkedList<T> _list = null; private SinglyNode _head = null; } }